The goal of this proposal is to rapidly but definitively investigate a new neurochemical avenue to help combat the decimation created by dependence on crack cocaine smoking. We propose an investigation of the efficacy of a promising putative stimulant abuse pharmacotherapy, captopril, as abstinence facilitation and relapse prevention treatment for crack cocaine dependence. The investigation will employ a placebo controlled, double-blind, random assignment, two cell parallel group design that will assess 80 subjects during 24 weeks of experimental treatment, with 3 follow-ups. We hypothesize that subjects on active captopril, but not placebo, will evidence: 1. Decreased crack cocaine abuse severity, operationalized as a decrease in crack cocaine use on quantitative GCMS in urine and on self-reported amounts and frequency of use, as increased control over crack cocaine craving, and as increased durations of abstinence and retention in drug treatment. 2. Increased utilization of formal and 12-step treatment services for crack cocaine abuse, operationalized using Natural History treatment exposure inventories. 3. Decreased multidimensional impairment operationalized as decreases of the non-drug dimensions of the Addiction Severity Index.